Retail sales, especially supermarket sales, include many sales of products by weight. Many items are placed in containers after selection by customers but before checkout. The weight of such a container when unloaded is known as the tare weight. Placing a loaded container on a scale to produce a weight reading generates a gross weight reading. The gross weight is the tare weight, that is, the weight of the empty container, plus the weight of the product or products. The tare weight must be subtracted from the gross weight to yield the net weight of the product or products being sold.
Containers may include plastic bags, paper bags, for example, for ground coffee or bulk candy, plastic trays, for example, for salads, and the like. For example, a supermarket may provide plastic bags in which customers may place produce, plastic containers in which customers may place salad bar or deli purchases, and the like. In order to comply with legal weight and measure requirements, retailers must deduct the tare weight of a container in which products sold by weight are placed from the gross weight on which the total price of the products is based. However, numerous different types of containers may be used, having different weights, and customers may place the same kinds of products in different kinds of containers having different weights. In addition, some customers may place a particular type of item, such as bananas or bell peppers in a container for purchase, while other customers may purchase such items without placing them into containers.
Many retailers simply deduct a container weight from all purchases of products sold by weight. However, if a customer does not place the products in a container, the retailer's practice of automatically deducting tare weight reduces the retailer's revenue because the retailer is deducting a container weight when no container is actually present. If the checkout transaction is performed by a retailer employee, it is possible to manually deduct the weights of the various containers, but this process adds time and complexity to the transaction. For low priced products in particular, the labor expense incurred in identifying a container and deducting its weight may be greater than the savings achieved. Consequently, in such cases, an automatic deduction in every case may be appropriate. In the case of a customer operated transaction, such as self checkout, the customer may be significantly inconvenienced if required to respond to questions about whether or not a container is being used and to determine and provide identification of the type of container being used.